exports.install = function (Vue, options) {
  Vue.prototype.is_string = function (href) {
    var childrenHref = window.sessionStorage.getItem('childrenHref')
    if (childrenHref) {
      childrenHref = JSON.parse(childrenHref)
      for (var i = 0; i < childrenHref.length; i++) {
        if (href === childrenHref[i].href) {
          return false
        }
      }
    }
    return true
  }
}
